“Marley fervently believes he was defending himself and that he was in danger of copping a hiding outside and that these guys had been into him all through the night.

“But the jury sat for two and a half hours and came up with a different verdict to that.”McGuire said Williams, 20, would return to the Albany District Court in April to be sentenced, where he faces a maximum 10 years in prison.

McGuire said Williams had been “in a good space” and praised his charity work.

“Marley’s a great young fella and has been doing wonderful work on the streets of Melbourne,” he said.“Time will tell, that’s why we have courts and a jury system.”

Williams’ family and supporters slumped in their seats and wept as the jury delivered the verdict following more than two-and-a-half hours of deliberations.

Williams been charged with grievous bodily harm over the attack on 29-year-old Matthew Robertson during the Christmas holidays in 2012, and the jury had been told they had the option of finding Williams guilty of the lesser charge of assault.

But the 12-person panel found Williams guilty of the more serious charge, which carries a possible maximum sentence of 10 years in prison.

He will be sentenced in April.

The Magpies defender had pleaded not guilty to a count of grievous bodily harm over the violence outside Studio 146, which began when Williams ran into three men, including Mr Robertson, in the toilets.

Williams told police he had been assaulted there, and “I wasn’t going to let them get the better of me’’.

But in court, he denied he had been angry and out for revenge when he hit Mr Robertson, claiming he feared for his own safety as the men approached him on the street.

“I threw a punch that I didn’t think about — it was a reflex punch. I threw it to tell them to back off,’’ Williams said.

“I was not intending to hurt anyone. It was more of a warning punch. It was either strike or be beaten up.’’

But prosecutors said Williams was acting out of “malicious, vindictive vengeance’’ when he swung the left-handed punch, which left Mr Robertson needing an emergency flight to Perth for surgery.

Prosecutor Tony Loudon said Williams attacked a man who was standing in an “utterly defensive position’’, posing no threat with his arms folded.

“He moves his weight to increase the power of his punch,’’ Mr Loudon said. “This was a powerful punch, and he was intending to put his whole body behind it.

“How is that reasonable to defend himself against a man with his arms folded?’’